Field of the Invention
The present technique relates to an image pickup apparatus.
Description of the Related Art
Image pickup apparatuses include a monolithic semiconductor device in which a single semiconductor layer constitutes a pixel circuit region and a peripheral circuit region. Different conditions are required to improve the characteristics of the pixel circuit region and the peripheral circuit region. More specifically, the pixel circuit region requires noise reduction in the pixel circuit, and the peripheral circuit region requires improved reliability of the peripheral circuit. It is known that hydrogen termination of a dangling bond on a surface of a semiconductor layer is effective in reducing noise in the pixel circuit region. However, the presence of hydrogen in the peripheral circuit region may be responsible for low reliability of the peripheral circuit. Thus, the characteristics of the pixel circuit region and the peripheral circuit region should be simultaneously improved.
Japanese Patent Laid-Open No. 2009-188068 discloses a solid-state image pickup element that includes a pixel unit, a peripheral circuit unit, and a passivation film disposed on the pixel unit and the peripheral circuit unit, wherein the passivation film serving as a hydrogen supply source is configured to have different residual hydrogen contents on the pixel unit and the peripheral circuit unit. It is stated that such a structure can ensure the reliability of a miniaturized transistor in the peripheral circuit unit with respect to temporal changes in threshold and satisfactorily decrease dark voltage on a surface of the pixel unit. The pixel unit and peripheral circuit unit in Japanese Patent Laid-Open No. 2009-188068 correspond to the pixel circuit region and peripheral circuit region in the present specification.
In the technique described in Japanese Patent Laid-Open No. 2009-188068, hydrogen supply to a semiconductor layer in an image pickup apparatus is not fully studied. In the image pickup apparatus according to Japanese Patent Laid-Open No. 2009-188068, the passivation film can prevent hydrogen diffusing from the passivation film to the semiconductor layer from diffusing into the outside (outside the image pickup apparatus). Thus, most of the hydrogen diffusing from the passivation film to the semiconductor layer is probably supplied to the semiconductor layer. Although not described in Japanese Patent Laid-Open No. 2009-188068, in the presence of a hydrogen supply source between the passivation film and the semiconductor layer, the passivation film can prevent hydrogen from diffusing from the hydrogen supply source to the outside. Thus, most of the hydrogen diffusing from the hydrogen supply source is probably supplied to the semiconductor layer. For these reasons, different residual hydrogen contents of the passivation film in the pixel circuit region and the peripheral circuit region are not sufficient to cause a great difference in the amount of hydrogen supplied to the semiconductor layer between the pixel circuit region and the peripheral circuit region. Consequently, the characteristics of the peripheral circuit unit cannot be improved.